Corrosion-resistant position measurement system and method of forming same

Abstract

A method of forming a position measurement system includes melting a surface of a substrate formed from a first material, wherein the surface defines at least one groove therein and wherein the surface is melted within the at least one groove. The method also includes, concurrent to melting, depositing a second material into the at least one groove to form a mixture of the first material and the second material. The method further includes solidifying the mixture to form an indicator material that is distinguishable from and metallurgically bonded to the first material, and depositing an alloy onto the substrate to form a corrosion-resistant cladding that covers the indicator material and the surface to thereby form the position measurement system. A position measurement system is also disclosed.

The invention claimed is: 
     
       1. A method of forming a position measurement system, the method comprising:
 machining a plurality of grooves in a surface of a shaft formed from a first material, the shaft defining an axis and having a shaft length that extends along the axis, the grooves having groove lengths that extend circumferentially about the axis, each of the plurality of grooves being axially spaced apart from an adjacent one of the plurality of grooves by one of a plurality of lands, wherein each groove has a substantially V-shape, a rounded vertex having a radius of from about 0.3 mm to about 0.7 mm, and two sides that define an angle therebetween of from about 55° to about 65°, the grooves having depths defined at the rounded vertexes, and the depths of the grooves being equal to one another; 
 laser welding a second material into only the plurality of grooves of the surface of the shaft, wherein the laser welding melts the surface within the plurality of grooves to form a mixture of the first material and the second material in only the plurality of grooves; 
 solidifying the mixture to form an indicator material that is distinguishable from the first material and metallurgically bonded in the plurality of grooves to the first material, wherein the indicator material is present in the grooves and is not present over the lands such that the indicator material is alternatingly present and not present along the shaft length of the shaft; and 
 depositing an alloy onto the shaft to form a corrosion-resistant cladding that covers the indicator material and the plurality of lands of the shaft to thereby form the position measurement system. 
 
     
     
       2. The method of  claim 1 , wherein the substrate has a longitudinal axis, and the plurality of grooves is disposed evenly along the longitudinal axis. 
     
     
       3. The method of  claim 2 , wherein a bond strength between the corrosion-resistant cladding and each of the indicator material and the first material is greater than or equal to 340 MPa. 
     
     
       4. The method of  claim 1 , further including finishing the corrosion-resistant cladding to define an external surface thereof, wherein the external surface is substantially smooth. 
     
     
       5. A method of forming a position measurement system, the method comprising:
 machining a surface of a cylindrical rod to define a plurality of grooves therein each having a substantially V-shape, the surface including a land disposed between adjacent grooves of the plurality of grooves, wherein the cylindrical rod is formed from a first material, the first material being magnetic; 
 laser welding a second material into only the plurality of grooves of the surface of the cylindrical rod, the second material being non-magnetic, wherein a non-magnetic indicator mixture of the first material and the second material is formed in each of the plurality of grooves; and 
 depositing a non-magnetic alloy onto the cylindrical rod to form a corrosion-resistant cladding that covers and is metallurgically bonded to each of the non-magnetic indicator material and the lands of the surface. 
 
     
     
       6. The method of  claim 5 , wherein a bond strength between the corrosion-resistant cladding and each of the non-magnetic indicator material and the first material is greater than or equal to 340 MPa. 
     
     
       7. The method of  claim 5 , wherein each of the plurality of grooves extends from the surface into the cylindrical rod at a depth of from about 0.09 mm to about 1.3 mm. 
     
     
       8. The method of  claim 7 , wherein each of the plurality of grooves has a groove width of from about 1.9 mm to about 2.1 mm, and wherein the land has a width of from about 1.9 mm to about 2.1 mm. 
     
     
       9. A position measurement system for a hydraulic cylinder comprising:
 a piston rod formed from a substrate material, the piston rod including a surface defining a plurality of grooves with each of the plurality of grooves being spaced apart from an adjacent one of the plurality of grooves by a land, wherein each of the plurality of grooves is substantially V-shaped; 
 an indicator material disposed in only the plurality of grooves of the surface, wherein the indicator material is different than the substrate material of the piston rod; and 
 a cladding disposed on the substrate so as to cover the indicator material and each land disposed between each of the plurality of grooves and the adjacent of the surface, wherein the cladding is metallurgically bonded directly to the indicator material and the lands of the surface. 
 
     
     
       10. The position measurement system of  claim 9 , wherein the cladding is metallurgically bonded to each of the indicator material and the surface at a bond strength of greater than about 340 MPa. 
     
     
       11. The position measurement system of  claim 9 , wherein the first material is magnetic and each of the corrosion-resistant cladding and the indicator material is non-magnetic. 
     
     
       12. The position measurement system of  claim 9 , wherein the plurality of grooves is distributed evenly along a longitudinal axis of the piston rod. 
     
     
       13. The position measurement system of  claim 12 , wherein each of the plurality of grooves extends from the surface into the piston rod at a depth of from about 0.09 mm to about 1.3 mm and each of the plurality of grooves has a groove width of from about 1.9 mm to about 2.1 mm, and wherein the land disposed between two adjacent grooves has a width of from about 1.9 mm to about 2.1 mm. 
     
     
       14. The position measurement system of  claim 9 , wherein the piston rod has a rod length that extends along an axis of the piston rod, and wherein the grooves are axially spaced-apart from one another along the rod length of the piston rod. 
     
     
       15. The position measurement system of  claim 14 , wherein the grooves have groove lengths that extend circumferentially about the axis of the piston rod and groove widths that extend axially along the axis of the piston rod, the groove lengths being longer than the groove widths. 
     
     
       16. The position measurement system of  claim 15 , wherein the lands are wider than the grooves when measured in a direction that extends along the axis of the piston rod. 
     
     
       17. The position measurement system of  claim 9 , wherein the lands form flat plateaus between the grooves when viewed in cross-section. 
     
     
       18. A method of forming a position measurement system, the method comprising:
 machining a plurality of grooves in a surface of a shaft formed from a first material, the shaft defining an axis and having a shaft length that extends along the axis, the grooves having groove lengths that extend circumferentially about the axis, each of the plurality of grooves being axially spaced apart from an adjacent one of the plurality of grooves by one of a plurality of lands; 
 laser welding a second material only into the plurality of grooves of the surface of the shaft wherein the laser welding melts the surface within the plurality of grooves to form a mixture of the first material and the second material in only the plurality of grooves; and 
 solidifying the mixture to form an indicator material that is magnetically distinguishable from the first material and metallurgically bonded in the plurality of grooves to the first material, wherein the indicator material is present in the grooves and is not present over the lands such that the indicator material is alternatingly present and not present along the shaft length of the shaft. 
 
     
     
       19. The method of  claim 18 , wherein the indicator material is non-magnetic or at least leas magnetic than the first material. 
     
     
       20. The method of  claim 18 , further comprising depositing an alloy onto the shaft to form a corrosion-resistant cladding that covers and directly contacts the indicator material present in the grooves and also covers and directly contacts the first material of the shaft at the plurality of lands of the shaft. 
     
     
       21. The method of  claim 20 , wherein the alloy is non-magnetic.